1. Field of the Invention
This application relates to a system and method that improves the SAGD facility with a system that can be added-on to an existing SAGD facility or as a new stand alone facility. The present invention relates to processes for producing steam from low quality rejected water containing high levels of dissolved inorganic solids or organics, such as oil.
Due to its simple direct contact, above ground adiabatic nature, combined with high pressure and temperature solid removal, the invention will minimize the amount of energy used to produce the mixture of steam and gas that is injected into the underground formation to recover heavy oil. This thermal efficiency minimizes the amount of greenhouse gases released into the atmosphere.
This thermal efficiency is achieved due to direct heat exchange. The condensed steam and the gases that will return back to the surface with the produced bitumen are at the temperature required for the oil recovery which is no higher than the underground reservoir temperature.
The present invention also relates to processes for making SAGD facilities more environmentally friendly by using low quality fuel and reducing the amount of greenhouse gas emissions by thermal efficiency and by injecting the CO2 into the formation, where a portion will remain permanently.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Steam injection into deep underground formations has proven to be an effective method for producing heavy oil. This is typically done by SAGD or by Cyclic Steam Injection (called “huff and puff”). In recent years, the SAGD method has become more popular, especially for heavy oil sand formations. Presently steam injection it is the only method that is commercially used on a large scale.
The present invention can be uses together with prior art processes currently used in upstream Upraders and down stream production facilities, which are currently in use by the industry, and adds the adiabatic direct contact steam and CO2 generation unit to reduce the disadvantages of the prior art and to allow for expansion with the use of a low quality water supply, the use of reject water from the existing facility and the use of low quality fuel supplies. There is also no need for high quality separation and purification downstream oil removal processes.
In the present invention, the exothermal reactions and the treatment of the injected gas mixture are done in an adiabatic control area above ground. The underground portion of oil production is very complex, with many unknowns as it was created over millions of years until it reached steady-state equilibrium. As was shown in other areas, one way to exploit resources and to produce products is by improving the organization and control. Since underground combustion processes change the chemistry of the reservoir, it is difficult to control and further complicates the already complicated underground reservoirs.
The injection of pure steam, or as a mixture with other gases, creates the minimum necessary increase in the underground formation disorder. It does not increase the complexity of the underground reservoir beyond the minimum required to mobilize the oil from the sand. This might be the reason why only injection of steam, or steam and other gases, are implemented and found to be commercially effective with SAGD.
The present invention is designed to be incorporated with SAGD. However, it can be useful with cyclic steam injection or with any other method for injection of steam into the ground. The main disadvantages of existing commercial SAGD are the main drivers.
SAGD consume large quantities of water to extract the heavy oil using steam. The water-to-oil ratio needed to produce the oil from the ground is in the range of 2-4 barrels of water to one barrel of oil. The current prior art technology requires relatively high water quality, as required by the once-through steam generators (OTSGs) or boilers for scaling prevention. The source water requires expensive purification processes that create sludge and reject water. As part of the recycled water treatment, all oil traces must be removed to treat the water both in lime softeners and evaporators and, as in the case of hot or warm lime softeners, significant amounts of waste sludge are created. The treatment requires significant purification of the water to prevent scaling in the steam generation units. Any oily emulsions must be broken down by chemicals or filters to a very high degree of separation. The process usually requires a stream of “reject water” from the blowdown that is injected into disposals wells or treated in an additional evaporators and crystallizers to evaporate the water from the reject water. Low quality, high TSS source water requires an expansive treatment facility and creates large amounts of sludge or disposal water. The oil producing companies are typically drawing water from an area which is much larger than the area from which the oil is produced. The water is pumped from relatively high aquifers to produce the best water quality available.
Due to environmental concerns regarding production of fossil fuels, a fossil water may be utilized. A fossil water is water that left the surface millions of years ago. Fossil water is found in deep underground formations and typically contains significant amounts of dissolved materials that make it unattractive for use by oil producers with current water treatment technologies as it is be far more expensive water treatment facility and produces large quantities of sludge and waste. There is a need to provide the oil producers with the ability to utilize fossil water while minimizing environmental impact.
The prior art SAGD required expensive water treatment plants and water de-oiling separation. This results in expensive facilities and chemicals to minimize oil traces in the recycled water. Reject water is produced and injected into disposal wells. In the case of lime softeners, sludge is produced as well. An increasing portion of the SAGD construction and operation costs is the cost of the water treatment plant. At present, the most widespread commercial water treatment process in the SAGD industry is the use of lime softeners. In this process, lime, magnesium oxide and other materials are used for removal of the dissolved solids in the form of a slurry. This process requires constant chemical supply and creates significant amounts of slurry waste resulting in landfill costs and environmental impacts. Different processes include evaporators that require water de-oiling and reject water that must be disposed of in disposal wells, or evaporated and crystallized to produce solid waste in additional facility. There is a need to be able to use oily water and water-oil emulsion for the production of steam so as to reduce the water treatment plant complexity and associated capital costs, and so as to reduce the amount of chemicals used. There is need to be able as part from the steam production process to cause the waste to be solid waste that is easy to handle.
SAGD consumes a large amount of heat energy. In most commercial SAGDs, natural gas is used as the energy source for the steam production. Natural gas is a valuable resource and the extensive use of it for producing oil is expensive with significant environmental impact. There is prior art that teaches the production of steam by other means. In some prior art, the steam is produced by burning some of the extracted heavy oil for the production of steam. This is a problematic process since there is a need for flue gas treatment prior to releasing it to the atmosphere. Another option combines upstream and downstream technologies in the form of an SAGD and upgrader that uses a gasification process to gasify the “barrel bottom” to produce syngas for the production of steam in the traditional way. Currently there is one commercial project that use this method. However, in the prior art, the steam generation is carried out by using co-generation, OTSG or boilers, where instead of burning natural gas for producing the steam, they burn the syngas as a source of energy. There is a need to use the heavy oil or the heavy asphaltin parts of the heavy oil for steam production.
In the prior art, a traditional gasifier is used to produce syngas. This is costly to install and operate and requires significant utilities to support it. The syngas is used as a fuel source to produce steam, using the traditional methods.
The SAGD technology consumes a significant amount of energy to produce the steam for the processes that are released to the atmosphere. The uses of OTSG, boilers or gas turbines with steam generation causes only a portion of the heat from the burning hydrocarbon to be injected underground to the reservoir. Flue gases and its carbon dioxide are released to the atmosphere. This issue becomes more and more significant due to global warming. There is a need to reduce carbon dioxide emissions as much as possible. The burning or gasification of other fuels or by-product waste will solve the problem of burning natural gas but it will not solve this issue since the amount of carbon dioxide released is equivalent to that released by burning natural gas. There is a need for minimizing the carbon dioxide release by: (1) using less steam; (2) producing the steam in an overall more efficient manner so as to minimize the aboveground heat losses; and (3) injecting the carbon dioxide with the produced steam to the reservoir where some of it will permanently remain. Down hole direct contact steam generators of the prior art produce steam by direct contact underground combustion process with water injection. These have several disadvantages. Any maintenance or cleaning requires a shut down of the wheel and drilling completion rigs to pull out the equipment. The water and fuel that is used must be of high quality so as to prevent the creation of solids that can plug the well over time. The maintenance of such systems is complicated. Any operation outside of optimal design conditions can have problems with corrosion and solids creation.
The above ground direct contact steam generators of the prior art generate reject water similar to the reject water generated by Once Through Steam Generation (OTSG). This system utilizes low quality water and low quality fuel. The reject water in the form of blowdown water can contain organic or inorganic materials. The blowdown can be either released to a disposal formation or crystallized to evaporate the remaining water. These prior art processes can not be integrated with prior art SAGD since they can not consume its reject flows or consume low quality solid fuels, such as coke or asphaltin.
It is an object of the present invention to provide a system and method that improves SAGD facilities by an add on to an existing SAGD facility.
It is another object of the present invention to provide a system and method that produces steam from low quality rejected water containing high levels of dissolved inorganic solids or organics.
It is another object of the present invention to provide a system and method that utilizes low grade fuel.
It is a further object of the present invention to provide a system and method that removes produced solids by converting the liquids to a gas phase under high pressures.
It is another object of the present invention to provide a system and method that minimizes the amount of energy used to produce the mixture of steam and gas that is injected into the underground formation to recover heavy oil.
It is a further object of the present invention to provide a system and method that minimize the amount of greenhouse gases that are released to the atmosphere.
It is still another object of the present invention to provide a system and method that enhance thermal efficiency as a result of direct heat exchange.
It is still a further object of the present invention to provide a system and method that serves to make the SAGD facilities more environmentally friendly by using low quality fuel and the reduction in greenhouse gases.
It is still a further object of the present invention to provide a system and method which minimizes water treatment costs.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.